PDFs with graphics instead of text

[KeenanFernandes2000]

If I use the PDFLoader and the pdf I upload has content but in the form of graphics,. How can I handle this type of document as it current throws an error when trying to convert it into a vector.

[dosubot[bot]]

🤖

Hey @KeenanFernandes2000, nice to see you back! Hope you're doing well.

The current implementation of the WebPDFLoader class in LangChainJS is designed to handle text content in PDFs. It uses the getTextContent() method from the pdf-parse library to extract text from each page of the PDF. This method does not handle graphical content, which is why you're seeing an error when trying to process PDFs with graphical content.

To handle PDFs that contain graphical content, you would need to use a different method or library that can extract or convert graphical content from PDFs. Unfortunately, the pdf-parse library used in this code does not support this functionality.

However, based on the provided context, the LangChainJS codebase has several methods that could potentially handle graphical content in PDFs. These methods are part of the PDFWorker and RenderTask classes.

1. PDFWorker class: This class controls the instantiation of PDF documents. It uses message handlers to pass information from the main thread to the worker thread and vice versa. Although it doesn't directly handle graphical content, it plays a crucial role in the rendering process.

2. RenderTask class: This class allows controlling of the rendering tasks. It has a method cancel() that can cancel the rendering task. It also has a property separateAnnots that indicates whether form fields are rendered separately from the main operatorList.

3. render() method: This method begins the process of rendering a page to the desired context. It returns a RenderTask object that contains a promise that is resolved when the page finishes rendering.

4. getViewport() method: This method returns a PageViewport object along with transforms required for rendering.

5. getAnnotations() method: This method returns a promise that is resolved with an array of the annotation objects. Annotations can include graphical content.

6. getOperatorList() method: This method returns a promise resolved with a PDFOperatorList object that represents the page's operator list. This list can include graphical operators.

These methods and classes could potentially handle graphical content in PDFs as part of the rendering process. However, this would require significant changes to the WebPDFLoader class and is beyond the scope of the current implementation.

You can find more information about these classes and methods in the langchain/src/types/pdf-parse.d.ts file.

Please note that modifying these classes or methods to handle graphical content in PDFs would require a deep understanding of the LangChainJS codebase and the pdf-parse library. It's also important to consider the potential impact on the performance and stability of your application.

I hope this information helps. If you have any further questions, feel free to ask.

Sources

• langchain/src/document_loaders/web/pdf.ts
• langchain/src/types/pdf-parse.d.ts

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